1. Field of the Invention
This invention relates to purification processes for photographic image-forming materials and more particularly to purification processes wherein said image-forming materials are nondiffusible sulfonamido compounds which are alkali-cleavable upon oxidation to release diffusible sulfonamido color-providing moieties.
2. Description Relative to the Prior Art
It is well known in the art to use image dye-providing sulfonamido materials in a photographic element wherein an imagewise exposed element can be contacted with an alkaline processing solution to effect an imagewise difference in mobility of at least a portion of the dye-providing sulfonamido material, i.e. to effect release of a dye or dye precursor, to render the compound insoluble or soluble. One such use of image dye-providing sulfonamido materials in color transfer processes is described by Fleckenstein in U.S. Pat. No. 4,076,529, issued Feb. 28, 1978 and Belgian Pat. No. 799,268, issued Feb. 28, 1973.
A method for preparing an image-forming sulfonamido compound is described in Example 42 of the above-noted U.S. Pat. No. 4,076,529 and comprises adding N-[5-hydroxy-8-(3-fluorosulfonylphenylazo)-1-naphthyl]methanesulfonamide to a solution of sodium bicarbonate and 1-amino-3-[2,4-bis(t-pentyl)phenoxybutylcarbamoyl]-4-hydroxynaphthalene in dimethylsulfoxide, under nitrogen.
The compound (designated magenta dye releasing compound XLIV) obtained in this Example has the formula: ##STR1## and is useful in photographic color diffusion transfer processes as a redox dye releaser. As described in U.S. Pat. No. 4,076,529, a redox dye releaser is characterized by its capacity to release a dye on reaction with oxidized deveoping agent in the presence of alkali. It is of course desirable that the redox dye releaser be as pure as possible. In fact, however, a redox dye releaser prepared by the reaction of a sulfonyl fluoride with an amino naphthol represented as follows: ##STR2## usually contains impurities which may be starting materials or derived compounds such as the oxidation products of 4-amino-1-naphthols.
It has been found that recrystallization alone does not always remove these impurities to the extent consistent with maximum photographic performance. For small samples, the various types of chromatography provide a ready solution to this problem but these techniques are not easily applied to large scale production.
In U.S. Pat. No. 3,236,643, issued Feb. 22, 1966, Husek noted the solubility of the claimed dye developers in dimethylformamide. However, these dye developers are isolated by precipitation in aqueous hydrochloric acid with no purification. Only the reaction intermediates are purified, and this procedure is accomplished by dissolving the intermediates in methyl Cellosolve and reprecipitating in water.
Canadian Pat. No. 917,648, issued Dec. 26, 1972 by Idelson, discloses the preparation of metal-dye complexes in a 1:10 mixture of dimethylformamide and methylene chloride. The product is isolated by pouring the reaction mixture into water and evaporating the methylene chloride. Purification is effected by reprecipitation of an acetone solution of the metal-dye complex in water.
In British Pat. No. 1,142,797, issued Aug. 19, 1965, Shipley describes a purification process for anthraquinone dye developers in a mixture comprising:
(1) dissolving an unpurified dye developer in a mixture comprising a water-soluble ketone and a small amount of strong mineral acid; PA1 (2) filtering the resulting solution to remove impurities which are acetone-insoluble; and PA1 (3) adding water to the filtered solution to precipitate the anthraquinone dye developer. PA1 a. preparing a first solution by dissolving an unpurified image-forming sulfonamido compound in an aprotic solvent; PA1 b. removing impurities from said first solution by, at least once: PA1 c. recovering purified image-forming sulfonamido compound from said first solution. PA1 a. evaporating said first solution to remove nonpolar, low-boiling solvent contamination; and PA1 b. precipitating said image-forming sulfonamido compound in a nonsolvent. PA1 a. preparing a third solution by adding a water-immiscible low-boiling solvent of intermediate polarity to said first solution; PA1 b. removing said aprotic solvent from said third solution by at least once: PA1 c. evaporating at least a portion of said water-immiscible low-boiling solvent of intermediate polarity from said third solution to effect crystallization of said purified image-forming sulfonamido compound. PA1 Ball is an organic ballasting group which renders said compound nondiffusible in a photographic element during development in an alkaline processing composition; PA1 Y represents the atoms necessary to complete a benzene, naphthalene or heterocyclic nucleus; and PA1 G is OR or NHR.sub.1 wherein R is hydrogen or a hydrolyzable moiety and R.sub.1 is hydrogen or an alkyl group of 1 to 22 carbon atoms, PA1 a. preparing a first solution by dissolving said nondiffusible sulfonamido compound in an aprotic solvent; PA1 b. removing impurities from said first solution by, at least once: PA1 c. recovering purified nondiffusible sulfonamido compound from said first solution. PA1 a. preparing a first solution by dissolving an unpurified image-forming sulfonamido compound in an aprotic solvent; PA1 b. removing impurities from said first solution by, at least once: PA1 c. recovering purified image-forming sulfonamido compound from said first solution. PA1 a. evaporating said first solution to remove nonpolar, low-boiling solvent contamination; and PA1 b. precipitating said image-forming sulfonamido compound in a nonsolvent. PA1 a. preparing a third solution by adding a water-immiscible low-boiling solvent of intermediate polarity to said first solution; PA1 b. removing said aprotic solvent from said third solution by at least once: PA1 c. evporating at least a portion of said water-immiscible low-boiling solvent of intermediate polarity from said third solution to effect crystallization of said purified image-forming sulfonamido compound. PA1 Col is a dye or dye precursor moiety.
However, this process is suitable only for removing impurities from anthraquinone dye developers which are acetone-insoluble. Acetone soluble dye releasers cannot be purified in this manner.
It is thus seen that a purification process suitable for large-scale manufacture of photographic image-forming sulfonamido compounds is extremely desirable. It is further seen that such a process should also remove acetone-soluble impurities.